text: import {
      createStackNavigator,
      createSwitchNavigator,
  } from 'react-navigation';
  import DetailsScreen from '../components/Details';
  import LoginScreen from '../components/Login';
  import HomeScreen from '../components/Home';
  import SettingsScreen from '../components/Settings';
  
  const AuthStack = createStackNavigator({
      Login: {
          screen: LoginScreen,
          navigationOptions: {
              header: null
          },
      },
  });
  
  const AppStack = createStackNavigator({
      Home: {
          screen: HomeScreen,
          navigationOptions: {
              header: null,
          },
      },
      Details: {
          screen: DetailsScreen,
      },
      Settings: {
          screen: SettingsScreen,
      },
  });
  
  export default createSwitchNavigator({
      Login: AuthStack,
      App: AppStack,
  }, {
      initialRouteName: 'Login'
  });